A prospective study of the impact of comorbid medical disease on bipolar disorder outcomes.
BACKGROUND
Several studies suggest that medical comorbidity is associated with worse clinical status in bipolar disorder. It is unclear which aspect of medical comorbidity is responsible: simple disease count, risk for future morbidity, or current physical burden.


METHODS
We analyzed three years of prospective data from a randomized clinical trial of collaborative care in 306 bipolar veterans. We examined the association of clinical outcome with baseline medical comorbidity defined as: (1) simple active disease count, (2) diseases with risk for future morbidity measured with the Charlson Comorbidity Index, and (3) current physical burden measured with the SF-36 Physical Component Summary score (PCS). Bipolar outcomes were weeks in episode, mean depression score, and change in mental health burden measured by the SF-36 Mental Component Summary score (MCS).


RESULTS
The three medical comorbidity measures were not highly correlated, indicating that each conveyed novel information. Controlling for potential confounders, worse baseline PCS predicted significantly higher mean depression scores (p=0.011) and less improvement in MCS scores (p=0.0099) over three years. Simple disease count and risk for future risk did not predict worse bipolar outcomes.


CONCLUSIONS
Some potential limitations include not accounting for all confounding factors, selection bias for participants, increased the likelihood of Type I error due to multiple comparisons and having a predominantly male population.


CONCLUSIONS
This long-term prospective study extends cross-sectional and retrospective research on the link between medical illness and bipolar outcomes. It is the current experience of burden of physical illness, rather than an unweighted or weighted disease count, that leads to worse bipolar outcomes.
Pirraglia
Paul A
PA
Providence VA Medical Center and the Warren Alpert Medical School of Brown University, United States. paul.pirraglia@va.gov
Biswas
Kousick
K
Kilbourne
Amy M
AM
Fenn
Howard
H
Bauer
Mark S
MS
D000328:Adult; D001714:Bipolar Disorder / Q000523:psychology*; D015897:Comorbidity; D017281:Cost of Illness; D003863:Depression / Q000523:psychology*; D004194:Disease / Q000523:psychology*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D009026:Mortality; D011446:Prospective Studies; D011788:Quality of Life / Q000523:psychology*; D016032:Randomized Controlled Trials as Topic; D012720:Severity of Illness Index